Purple Loosestrife

CIPC – Priority Invasive Plants

Purple Loosestrife

Purple loosestrife (Lythrum salicaria) can be found growing in open riparian areas and wetlands throughout Vancouver Island and surrounding coastal communities. Introduced as a garden ornamental, due to its vibrant purple flowers perched on top of a tall stem, this beautiful plant aggressively crowds out native vegetation, impacting native plants, amphibians, birds and other wetland species. Purple loosestrife is estimated to be spreading at a rate of 115,000 hectares per year in the United States, destroying valuable wetlands.

Each plant is capable of producing up to 2.5 million seeds that can be dispersed by wind, water, wildlife, and humans. Plants can also reproduce from root fragments.

The best way to identify purple loosestrife is by its square stems (roll it in your fingers) and opposite leaves. If you have purple loosestrife in your garden, remove it immediately. Pull or dig the plants out and ensure that all root fragments are removed to prevent re-growth. For large patches, there are relatively effective biocontrol agents, Galerucella calmariensis and pusilla. These beetles feed on the plant stems in their larval stage. For more information on biocontrol, see http://www.entomology.wisc.edu/mbcn/kyf501.html.